President Obama has boxed himself in. He can no longer ignore his own proclamation of a “red line.” The chairman of the Joint Chiefs of Staff, in a breach of proper civil-military relations, has publicly telegraphed his skepticism about any use of force in Syria. But the scale, openness and callousness of the Syrian government’s breaking of an important taboo seems likely to compel this president — so proud of his record as a putative war-ender — to launch the warplanes yet again in the Middle East.

The temptation here is to follow the Clinton administration’s course — a futile salvo of cruise missiles, followed by self-congratulation and an attempt to change the topic. It would not work here. A minority regime fighting for its life, as Bashar al-Assad’s is, can weather a couple of dozen big bangs. More important, no one — friends, enemies or neutrals — would be fooled. As weak as the United States now appears in the region and beyond, we would look weaker yet if we chose to act ineffectively. A bout of therapeutic bombing is an even more feckless course of action than a principled refusal to act altogether.

A serious bombing campaign would have substantial targets — most plausibly the Syrian air force, the service once headed by Assad’s father, which gives the regime much of its edge over the rebels, as well as the air defense system and the country’s airports, through which aid arrives from Iran. But should the Obama administration choose any kind of bombing campaign, it needs to face some hard facts.

For one thing, and despite the hopes of some proponents of an air campaign, this would not be surgical. No serious application of air power ever is, despite administration officials’ claims about the drone campaign, which, as we now know, has killed plenty of civilians. A serious bombing campaign means civilian casualties, at our hands. And it may mean U.S. and allied casualties too, because the idea of a serious military effort without risk is fatuous.

The administration would need congressional authorization. Despite his professed commitment to transparency and constitutional niceties, Obama has proved himself reluctant to secure congressional authorization for the use of force, most notably with Libya in 2011. Even if an authorization is conferred retroactively, it needs to be done here because this would be a large use of force; indeed, an act of war.

And it probably would not end cleanly. When the president proclaimed the impending conclusion of the war with al-Qaeda, he disregarded the cardinal fact of strategy: It is (at least) a two-sided game. The other side, not we, gets to decide when it ends. And in this case neither the Syrian government nor its Iranian patrons, nor its Hezbollah, Russian and Chinese allies, may choose to shrug off a bombing campaign. Chess players who think one move ahead usually lose; so do presidents who think they can launch a day or two of strikes and then walk away with a win. The repercussions may be felt in neighboring countries; they may even be felt in the United States, and there is no excuse for ignoring that fact.

Despite all these facts, not to act would be, at this point and by the administration’s own standards, intolerable.

The slaughter in Syria, tolerated for so long, now approaches the same order of magnitude (with the number of dead totaling six figures at least) as Rwanda, but in a strategically more important place. Already it is late, perhaps too late, to prevent Syria from becoming the new Afghanistan or Yemen, home to rabidly anti-Western jihadis. A critical firebreak, the use of chemical weapons on a large scale, has been breached.

No less important, U.S. prestige is on the line. Why should anyone, anywhere, take Obama’s threats (or for that matter, his promises) seriously if he does nothing here? Not to act is to decide, and to decide for an even worse outcome than the one that awaits us.

“War is an option of difficulties,” a British general once remarked. The question before the president is whether he will make matters worse by convincing himself that he has found a minimal solution to a fiendish problem. He will convince no one else.

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Comments our editors find particularly useful or relevant are displayed in Top Comments, as are comments by users with these badges: . Replies to those posts appear here, as well as posts by staff writers.